.box {
    margin: 10px;
    width: 100px;
    height: 100px;
    display: inline-block;
    text-align: center;
    padding-top: 30px;
    background-color: skyblue;
    font-size: 10px;
    box-sizing: border-box;
}

.box2 {
    margin: 10px;
    width: 150px;
    height: 100px;
    display: inline-block;
    text-align: center;
    padding-top: 30px;
    background-color: seagreen;
    font-size: 10px;
    box-sizing: border-box;
}

.border-box {
    margin: 10px;
    width: 300px;
    height: 200px;
    display: inline-block;
    text-align: center;
    padding-top: 30px;
    font-size: 10px;
    box-sizing: border-box;
    border: 2px solid black;
}

.jianbian {
    background: #2193b0;
    /* fallback for old browsers */
    background: -webkit-linear-gradient(to right, #6dd5ed, #2193b0);
    /* Chrome 10-25, Safari 5.1-6 */
    background: linear-gradient(to right, #6dd5ed, #2193b0);
    /* W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */

}

.circle-box {
    margin: 10px;
    width: 200px;
    height: 200px;
    border: solid 2px black;
    border-radius: 50%;
    display: inline-block;
    text-align: center;
    padding-top: 30px;
    font-size: 10px;
    box-sizing: border-box;
}

.all-center {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
}

.start-center {
    display: flex;
    justify-content: start;
    align-items: center;
    flex-wrap: wrap;
}

.relative {
    position: relative;
    top: 0;
    left: 0;
}

.absolute {
    position: absolute;

}